1. Field of the Invention
This invention relates to the fields of diagnosis and drug delivery. More particularly it relates to medical devices and methods capable of monitoring levels of a bodily fluid analyte and optionally releasing of appropriate therapeutic agents.
2. Background
“Point of care” devices that are capable of detecting biological macromolecular activity or drug concentration levels are in high demand because they eliminate the need for patient lab visits, thus providing savings in both time and expense. One of the most valuable aspects of modern microarray technology is the ability to detect biological macromolecular dysfunction, malformation or mutation resulting in disease. However, this capability has not been fully exploited because such arrays have not been incorporated into ingestible, implantable or wearable point of care devices. Modern microarray technology is limited to characterization of biological macromolecules and their metabolites by analysis of immobilized analytes stabilized on slides to be inserted into a machine or analyzed manually outside of living organisms.
Because whole blood contains cells, platelets, a myriad of proteins and other macromolecules, assays involving blood typically require pre-processing of the sample to remove these components. Integrating pre-processing steps into a point of care device drives up the cost of the device itself, thus making use of the device financially unviable. For example, some devices currently on the market using whole blood in their assays; among them are Boehringer Mannheim's Reflotron™ system for measuring blood borne analytes (most notably cholesterol) and the iStat™ (iStat Inc.), which performs a number of critical care assays, including electrolytes, general chemistries, blood gases and hematology. The Reflotron™ relies on dry chemistry technology in which enzymes or other reactive elements are immobilized on the surface of a test strip. The assay is a calorimetric activity assay in which the reaction produces a color change and is thus indicative of the amount of analyte present. The iStat™ relies on electrochemical detection to produce a signal. In either case, a blood sample is taken separately (typically by a finger prick) and then placed on the chip (or cartridge in the case of the istat), where the reaction occurs and is analyzed by an external detection unit These existing monitoring systems are insufficient and inconvenient as they usually require the user to prick themselves and multiple steps to obtain a result. As such, there is a need for a wearable device that can repeatedly, automatically and accurately monitor bodily fluids such as blood.
Point of care devices are also useful in certain situations where systemic biological samples such as blood, urine or stool, cannot provide adequate information as to subtle molecular changes at the situs of disease. In such a case, even if the clinician could pinpoint the exact situs of an ailment, obtaining a biological sample for analysis comes only at great risk, pain and expense for the patient. Additionally, a point of care device would be desirable where the systemic administration of drug agents, such as by transdermal or intravenous means, treats the body as a whole even though the disease to be treated may be localized. Here, systemic administration may not be desirable because the drug agents often have unwanted effects on parts of the body that are not intended to be treated, or because treatment of the diseased part of the body requires a high concentration of drug agent that may not be achievable by systemic administration. For example, when administered to a patient systemically, some drugs (e.g., chemotherapeutic drugs such as those used to treat cancer and other proliferative disorders) may cause undesirable side effects. It is therefore often desirable to detect disease and administer drug agents at a localized site within the body.
As such there is a demand for point of care devices capable of detecting biological macromolecular activity or drug concentration levels that may also administer a specific therapeutic agent at a localized site within the body in response to changes in biological macromolecular activity or drug concentration levels. All articles, publications and patents cited herein are incorporated by reference in their entirety for all purposes. Additionally, provisional patent application Ser. No. 60/501,847 filed Sep. 11, 2003, is hereby incorporated by reference.